In a microwave system, modulation signals have different amplitudes on the time domain, and suffer different non-linear distortion after passing through a PA (Power Amplifier, power amplifier) device. According to the distortion condition, a digital pre-distortion (Digital Pre-Distortion, DPD) non-linear distortion compensation coefficient is obtained, and the DPD non-linear distortion compensation coefficient is added in the data flow that passes through the PA device. After undergoing power amplification, the data flow counteracts the non-linear features of the PA device, thereby implementing non-linear distortion counteraction of the PA device and making the gain curve of the PA device closer to an ideal curve.
In the prior art, a receiving device receives different signal-distorted data flows generated after the data flows pass through the PA device, and a hard decision module determines the actual position (that is, actual constellation point) of each symbol on the constellation map according to the position of each constellation point on the constellation map corresponding to the modulation mode of the data flow, where each symbol corresponds to each piece of data in the data flow. After being processed by the hard decision module, the data flow enters the DPD. At the DPD, a pre-distortion parameter is obtained according to the difference between the ideal constellation point and the actual constellation point, so that the non-linear distortion of the PA device can be counteracted according to the pre-distortion parameter.
However, when the modulation mode is QPSK (Quadrature Phase Shift Keying, quadrature phase shift keying), the amplitude on the time domain does not differ between modulation signals. Consequently, the DPD non-linear distortion compensation coefficient in QPSK mode is not available according to the prior art.